Problem with logical indexing

I'm trying to write a function that will take a row vector of temperatures as input and will give the number of temperatures below 32° as output. I have tried this:

function numfreeze = freeezing(temperatures)
numfreeze = numel(freezing(freezing<32))
end

...but I get the error message "Out of memory. The likely cause is an infinite recursion within the program."

Can someone help me and tell me what this means? When I just use

numfreeze = numel(freezing(freezing<32))

in the command window after setting a vector for "temperatures", it works fine.

Answer 1

[Guillaume]

freezing is the name of the function. So when you write freezing inside the function, you're telling it to call itself. Of course, once it's called itself, it reexecute that freezing call ad finitum. Hence the infinite recursion.

You probably meant to use the input variable temperatures inside that function

function numfreeze = freeezing(temperatures)
    numfreeze = numel(temperatures(temperatures<32))
end

While the above will work, it's not the most efficient. You're deleting all the elements above 32 to then find out how many remain. It be simpler to just count how many true values are in your logical array and not bother with the deletion, so:

function numfreeze = freeezing(temperatures)
    numfreeze = nnz(temperatures<32);  %you can also use sum instead of nnz
end

[RP]

Thank you so much, this works and I didn't know nnz before!

Answer 2

[Alex Mcaulley]

I think you have a typo, calling infinite times the function freezing, then:

function numfreeze = freeezing(temperatures)
    numfreeze = numel(temperatures(temperatures<32))
end

Answer 3

[Ajith Thomas]

function numfreeze=freezing(w)
lowerthan_32=w(w<32);
no_logical_values=lowerthan_32(lowerthan_32>=0);
numfreeze=length(no_logical_values);
end

[Ajith Thomas]

function numfreeze=freezing(w)
lowerthan_32=w(w<32);
numfreeze=numel(lowerthan_32);
end